Method of preparing material for lithium secondary battery of high performance

Abstract

Provided is a method for preparing a lithium mixed transition metal oxide, comprising subjecting Li 2 CO 3 and a mixed transition metal precursor to a solid-state reaction under an oxygen-deficient atmosphere with an oxygen concentration of 10 to 50% to thereby prepare a powdered lithium mixed transition metal oxide having a composition represented by Formula I of Li x M y O 2 wherein M, x and y are as defined in the specification. Therefore, since the high-Ni lithium mixed transition metal oxide having a given composition can be prepared by a simple solid-state reaction in air, using a raw material that is cheap and easy to handle, the present invention enables industrial-scale production of the lithium mixed transition metal oxide with significantly decreased production costs and high production efficiency. Further, the thus-produced lithium mixed transition metal oxide is substantially free of impurities, and therefore can exert a high capacity and excellent cycle stability, in conjunction with significantly improved storage stability and high-temperature stability.

What is claimed is: 
     
       1. A method for preparing a lithium mixed transition metal oxide, comprising subjecting Li 2 CO 3  and a mixed transition metal precursor to a solid-state reaction under an oxygen-deficient atmosphere having an oxygen concentration of 10 to 50% by volume to thereby prepare a powdered lithium mixed transition metal oxide having a composition represented by Formula I:
   Li x M y O 2   (I)
 
 wherein: 
 M=M′ 1−k A k , wherein M′ is Ni 1−a−b (Ni 1/2 Mn 1/2 ) a Co b , 0.65≦a+b≦0.85 and 0.1≦b≦0.4; 
 A is a dopant; 
 0≦k<0.05; and 
 x+y=2 and 0.95≦x≦1.05, 
 wherein the mixed transition metal precursor has a tap density of 1.1 to 1.6 g/cm 3 . 
 
     
     
       2. The method according to  claim 1 , wherein the oxygen concentration is 10% to 30% by volume. 
     
     
       3. The method according to  claim 2 , wherein the atmosphere is an air atmosphere. 
     
     
       4. The method according to  claim 1 , wherein the mixed transition metal precursor is at least one selected from the group consisting of M(OH) 2  and MOOH. 
     
     
       5. The method according to  claim 4 , wherein the mixed transition metal precursor is MOOH, and is prepared by an ammonia-free process. 
     
     
       6. The method according to  claim 1 , wherein a mixing ratio of Li 2 CO 3  and the mixed transition metal precursor is 0.95 to 1.04:1 wherein the ratio of Li 2 CO 3 :mixed transition metal precursor is a w/w ratio. 
     
     
       7. The method according to  claim 1 , wherein the solid-state reaction includes a sintering process at 600 to 1,100° C. for 3 to 20 hours. 
     
     
       8. The method according to  claim 7 , wherein an amount of air exceeding 2 m 3 /kg LiMO 2  during the sintering process is supplied to a reaction vessel equipped with a heat exchanger for pre-warming of the air. 
     
     
       9. The method according to  claim 1 , wherein the lithium mixed transition metal oxide is prepared by a large-scale process of 5 kg or more wherein at least 2 m 3  of air per 1 kg of the lithium mixed transition metal oxide is pumped into or out of a reaction vessel, wherein the at least 2 m 3  of air is the volume measured at room temperature. 
     
     
       10. The method according to  claim 9 , wherein at least 10 m 3  of air for 10 hours per 1 kg of the lithium mixed transition metal oxide is pumped into or out of the reaction vessel, wherein the at least 10 m 3  of air is the volume measured at room temperature. 
     
     
       11. The method according to  claim 8 , wherein the heat exchanger pre-warms in-flowing air before the in-flowing air enters the reaction vessel, while cooling out-flowing air.